1. Field of the Invention
The present invention relates to a paper-feeding roller and more particularly to a paper-feeding roller composed of a rubber composition containing short fibers. The orientation of the short fiber is improved to thereby suppress a variation in the friction coefficient of the surface of the paper-feeding roller.
2. Description of the Related Art
A paper-feeding rubber roller is used for paper-feeding mechanisms such as various types of printers, an electrostatic copying machine, a facsimile apparatus, an automatic teller machine (ATM) and the like. The paper-feeding roller of the present invention means a paper supply roller which transports paper owing to the rotation thereof and the friction between the surface thereof and paper with the paper supply roller in contact with the paper, a resist roller, and a paper-feeding roller and/or a transcribe roller. The coefficient of friction of the surface of the paper-feeding roller is affected adversely by foreign matters which have attached to the surface thereof. For example, a problem occurs that when paper powder attaches to the surface of the paper-feeding roller, the paper is faultily transported.
To overcome the above-described problem, a paper-feeding roller composed of a rubber composition containing a glass fiber is proposed, as disclosed in the patent document 1. A part of the glass fiber is disposed on the surface of the paper-feeding roller to expose the glass fiber partly. The exposed portion of the glass fiber has an effect of scratching the surface of paper. The paper-scratching effect is hardly obstructed by the paper powder that has attached to the surface of the paper-feeding roller, thus making it possible to reduce the degree of faulty transport of paper.
The rubber composition containing the short fiber becomes hard. Consequently the area of contact between the paper-feeding roller and the paper decreases. Thus the coefficient of friction of the surface of the paper-feeding roller tends to become low. However, the paper-feeding roller is capable of sufficiently performing its function when it has a coefficient of friction necessary for transporting the paper and is not demanded to have a higher coefficient of friction.
In recent years, owing to the progress of the color printing technique and a growing demand for forming a high-quality image, in various types of printers, polymerization toner has come to be used instead of conventional toner manufactured by a pulverizing method. The polymerization toner has a small particle size distribution. Even small-diameter particles of the polymerization toner have a high flowability. Thus the polymerization toner allows a high transfer efficiency to be obtained and a high-quality image to be formed. Therefore it is conceivable that high-performance printers using the polymerization toner will be popular in the future.
However, paper is faultily transported in various types of printers in which the polymerization toner is used and a paper-feeding roller composed of the rubber composition containing the glass fiber is mounted.
The main reason for the faulty transport of paper is as follows: The polymerization toner is formed by chemically fusing low-molecular-weight resin, consisting of finely divided particles, formed by emulsion polymerization, a pigment, and paraffin wax together. The resin having a low molecular weight and the wax attach to the rubber roller readily. This indicates that the addition of the glass fiber to the rubber composition is insufficient for preventing the polymerization toner and the wax from attaching to the surface of the rubber roller.
Patent document 1: Japanese Patent Application Laid-Open No. 2002-145466